The objectves of the propsed research are to characterize kinetically and pharmacologically some of the active transport systems in the choroid plexus of the lateral ventricles that are responsible for the formation of the CSF and for the maintenance of the constancy of the composition of this fluid. The present studies include the role of the choroid plexus in regulating the (Ca) in the CSF, the possible role of prolactin in regulating choroid plexus function and the role of the various ATPases in choroid plexus transport.